# vector multiplication.

#### .ash.

##### New Member
hi, i need help in knowing how to use an array formula for the following (and even help in knowing if i need an array formula!)

i have my data in pairs like this: (ax1, by1),(cx2, dy2),...
(im using the numbers 1,2,3... only as index to denote the pair, not as powers!)
and in excel i have A1=a, B1=b, A2=c, B2=d so i have the coefficients for all X in column A and for Y in column B.
what i need is to multiply the following:
(ax + by) * (cx + dy) * (ex + fy) * ....

as you know, the result is the summation of the multiplication of the combinations, something like:
(a*c*e)x^3 + (a*c*f)x^2y + (a*d*e)x^2y + ...
for the case with 3 pairs.

how can i get not only the total summation but also see the results of each partial multiplication above?

hope i made my situation clear. do i need arrays? do i need VB?

i will deeply appreciate any help.
thanks

### Excel Facts

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#### .ash.

##### New Member
binomials

sorry i meant binomials multiplication